Real-time control of wetlands alters waterbird activity and water quality outcomes

Poorly performing stormwater constructed wetlands are becoming increasingly common. Flow management through these systems by real-time control has potential to improve hydrologic and treatment performance. Previous research has attributed net pathogen export from constructed wetlands to waterbirds, but the water quality impacts of their in-wetland activity remain unclear. Further, the impact of flow controls on local waterbirds and water quality in constructed wetlands has yet to be investigated. Traditional waterbird monitoring requires extensive investments, limiting high resolution monitoring capabilities. This study develops and uses a pre-trained image analysis model to provide high spatial and temporal resolution of waterbird activity within a constructed wetland and investigates the impact of real-time control on waterbird activity and associated water quality impacts. Real-time control of wetland water level increased waterbird occurrence 4.6-fold per 5 cm drop in water level 20 to 30 cm below natural water level (NWL) where bed sediments were exposed. When antecedent temperatures were above 20 °C waterbird interaction with the wetland was significantly correlated with effluent Campylobacter spp. (0.92, p = 0.025) but not E. coli concentrations. In conditions below 20 °C, Campylobacter spp. concentrations increased by 1.0 log from inlet to outlet and high flows were the most correlated with effluent concentration, but no factors had significant correlation during these colder periods. During colder periods, proactive wetland draining prior to a rainfall event is likely beneficial to reduce peak flow and resuspension of contaminated bed sediments, possibly yielding lower microbial concentrations at the outlet.